1. Field of the Invention
The present invention relates to an ink jet recording device that performs printing operations by ejecting ink from nozzles, and to a method of controlling the same.
2. Description of Related Art
Generally, a print engine for a serial-print ink jet printer includes a head, a carriage, and a sheet-feed mechanism. The head is provided with a row of nozzles for ejecting ink, and is mounted on the carriage. The sheet-feed mechanism feeds a sheet past the carriage so that the carriage is positioned in confrontation with the sheet. The carriage is oriented so that the nozzle row is aligned with the sheet-feed direction of the print sheets.
To print on a print sheet, the carriage is transported, that is, scanned, in a direction perpendicular with the sheet-feed direction. While the carriage is scanned across the print sheet, ink is ejected from the nozzles onto the print sheet, so that printing is performed in a predetermined region of the print sheet. The print sheet is then fed in the sheet-feed direction until the next region is aligned with the print head, whereupon the next region is printed on by scanning the carriage across the print sheet. By repeating these operations, the entire print sheet is printed on.
When the head of such a print engine is not used for long periods of time, ink around the nozzles can dry out and clog the nozzles or change the ink ejection characteristics of the nozzles. This reduces print quality. The print engine is therefore provided with a head cap and a refresh mechanism to prevent this problem.
The head cap is located outside from the region that the carriage moves during printing. The ink in nozzles can be prevented from drying out by covering the head with the head cap while the print engine is not printing.
With the refresh mechanism, each time a predetermined duration of time elapses, printing operations are terminated and the print head is transported to outside the printing region. Then, ink is ejected from all of the nozzles in what is called a refresh operation. By performing such a refresh operation, ink is ejected from nozzles that have not been used for printing, so that ink in these nozzles can be prevented from drying out.
However, printing operations must be stopped each time the predetermined duration of time elapses so that the print head can be transported outside the printing region and so a refresh operation can be performed. This reduces printing speed. Also, ink is ejected from all nozzles during a refresh operation, even from nozzles without risk of being clogged by dried ink. This wastes ink.
It is an objective of the present invention to overcome the above-described problems, and provide an ink jet printer and a method of controlling the same to require no, or fewer, refresh operations that require termination of printing operations, thereby reducing the amount that printing speed is reduced and reducing consumption of ink.
In order to attain the above and other objects, the present invention provides an ink jet recording device, comprising: a print head formed with a plurality of nozzles arranged in a first predetermined direction; a print head scanning mechanism scanning the print head in a second predetermined direction substantially perpendicular to the first predetermined direction; a sheet feeding mechanism feeding a print sheet relative to the print head in a sheet feeding direction that is substantially parallel to the first predetermined direction; a print engine driving the print head to perform successive scan printing operations to eject ink from the nozzle, the print engine driving the sheet feeding mechanism to feed the print sheet before controlling the print head to perform each scan printing operation: and a print controller controlling the print engine, the print controller including a scan data preparation processor preparing scan data for each scan printing operation, based on the nozzle configuration of the print head and based on print data; a sheet transportation processor controlling a sheet feed amount, by which the sheet feeding mechanism feeds the print sheet; a detecting unit detecting how each nozzle is used in the successive scan printing operations; and a scan data rewriting unit rewriting the scan data and changing the amount of sheet feed selectively based on the detected result.
The detecting unit may detect, before starting one scan printing operation, whether some nozzle has not been used for a predetermined period of time. When the detecting unit detests some unused nozzle that has not been used for the predetermined period of time, the scan data rewriting unit may rewrite the scan data for the subject scanning operation so as to use the detected unused nozzle during the subject scanning operation, and change, from a predetermined amount, the amount of sheet feed, by which the sheet is to be fed before the subject scan printing operation, in accordance with the rewritten scan data. When the detecting unit detects no unused nozzle, the scan data rewriting unit may perform no rewriting operation and perform no sheet feed amount changing operation.
Alternatively, the scan data rewriting unit may rewrite the scan data so that each nozzle will be used at least once while several scan printing operations are successively conducted to print a predetermined number of page""s worth of image.
For example, the detecting unit may detect, before starting the several scan printing operations to print the predetermined number of page""s worth of image, whether some nozzle will be used less than a threshold number of times. When the detecting unit detects that some nozzle will be used less than the threshold number of times, the scan data rewriting unit may rewrite the scan data for the several scan printing operations so as to use the detected nozzle at least the threshold number of times during the several scan printing operations, and change the amount of sheet feed, by which the sheet is to be fed during the several scan printing operations, based on the rewritten scan data.
According to another aspect, the present invention provides a method of controlling an ink jet recording device, the ink jet recording device including: a print head formed with a plurality of nozzles arranged in a first predetermined direction; a print head scanning mechanism scanning the print head in a second predetermined direction substantially perpendicular to the first predetermined direction; a sheet feeding mechanism feeding a print sheet relative to the print head in a sheet feeding direction that is substantially parallel to the first predetermined direction; and a print engine driving the print head to perform successive scan printing operations to eject ink from the nozzles, the print engine driving the sheet feeding mechanism to feed the print sheet before controlling the print head to perform each scan printing operation; the method comprising the steps of: preparing scan data for each scan printing operation, based on the nozzle configuration of the print head and based on print data; detecting how each nozzle is used in the successive scan printing operations; rewriting the scan data and changing the amount of sheet feed selectively based an the detected result; and controlling the print engine to drive the sheet feeding mechanism to feed the print sheet by the selectively-rewritten sheet feed amount, and controlling the print engine to drive the print heed to eject ink based on the selectively-rewritten scan data.